It is conventional to test automotive and other internal combustion engines either by driving the engine under its own power or by connecting the crankshaft of the engine to an electric or other driving motor which enables the rotary and reciprocatory parts of the engine under test to be driven.
Testing of an engine that is operated under its own power requires the use of some mechanism, such as a dynamometer, for the imposition of loads on the engine. The dynamometer conventionally is either an A.C. or D.C. generator or prony brake. The necessity of using a dynamometer increases the cost and time required to test an engine.
The testing of an engine while it is being operated under its own power enables a number of tests to be performed, such as horsepower output, fuel consumption, exhaust emissions, and the like. However, the operation of an engine under its own power requires the provision of means to supply fuel, coolant, lubrication, and noise abatement apparatus. In addition, the operation of an engine under its own power necessitates the provision of elaborate ventilation systems to accommodate the engine exhaust.
Although the testing of an engine operating under its own power enables a good many desirable tests to be performed, the integrity tests that can be imposed on the valve train, camshaft, crankshaft, engine block, and head are limited because of the engine's tendency to stall when the load on the engine is increased beyond the level that the engine can accommodate. In addition, certain defects, such as faulty valves and piston rings, are not always detectable during operation of the engine at relatively low operating speeds, unless the faults are of substantial proportions.
Driving an engine by some means other than under its own power is known as motoring the engine. Motoring of an engine does not enable tests such as horsepower output, fuel consumption, exhaust emissions, and the like to be performed, but a great many other tests can be performed by motoring the engine. Motoring the engine also dispenses with the need for fuel storage and delivery systems and obviates the need for exhaust ventilation systems.